Refining cracked gasoline



Aug. 7, 1934.

K'. J. SMITH REFINING CRACKED GASOLINE Filed Jan. 10, 1930 WMV /B Y I I L l QJ@ Y ATTORN EY Patented Aug. 7, 1934 PATENT oFFice-E 1,909,047 REFINTNG CRACKED GAsoLnvE Kenneth J. Smith, l Dorado, Kans., assignor to Skelly Oil Company, Wilmingto poration of Delaware n, Del., a corappiicatioa January 10, 1990, smal No. 419,800

Claims.

This invention'relates to improvements in the reiining of gasoline intended for use as motor i'uel and more particularly relates to the treatment of gasoline produced b'ysevere cracking operi .ins to repress the formation `of gum in the gasoline product. i Gasoline produced by vapor phase cracking operations in which higher boiling oil is heated to a high cracking temperature approximating 1000 F. or higher under relativelylowr superatmospheric pressure, for example, is of special value as a. motor fuel because'it includes constituents imparting anti-knock properties to the gasoline product. Such gasoline,` however, also l5 usually includes substantial quantities of gum or gum-forming constituents as wellas these antiknock constituents. This invention provides an improved method o! treating such gasoline, `pro duced by such vapor phase cracking operation or other severe cracking operation `wherein similarly severe cracking temperatures are employed but in which cracking may not be effected exclusively in the vapor phase because of the maintenance of a somewhathigher pressure in theV S0 oil including a maj or proportion of oil components higher boiling than suitable as components of gasoline` and having a solvent capacity for such gum or gum-forming constituents is maintained at a temperature upwards of` about 650 F. promoting the polymerization of such gum or gumforming constituents to form higher boiling polymers, a stock or 'stock mixture including such higher boiling oil components as well as a substantial proportion 'oi' the gasoline product of a 40 severe cracking operation containing'substantial quantities of gum or gum-forming constituents to be rened is supplied to this bodyof oil, vapors including the vaporized gasoline product are taken 01T from this body of oil and subjected to' a refluxing operation .from which higher boiling condensate is returned to thisbody of oil, the vaporized gasoline product or a vapor mixture including this gasoline product/is taken ou from the reiiuxing operation and a refined gasoline product'is collected therefrom, and unvaporized oil including such gum constituents and polymers of such gum or gum-forming constituents in solution is discharged from this body of oil. This body oi oil may be maintained at a temperature at which some further cracking oi the stock or stock mixture supplied thereto take place in the operation, but it is more advantageously malntained at a temperature below that at which any substantial cracking of the stock or stock mixture supplied to the operation begins.

The invention will be further described in connection with the accompanying drawing which illustrates, diagrammatically, one form o! apparatus adapted for carrying out the process of the invention, but it will be understood that reference is made to this particular form of apparatus only to illustrate the invention and that the invention can be carried out in other and different apparatus.

The apparatus illustrated comprises a still 1 70 adapted to be operated under superatmospheric pressure, a reilux tower 2 connected to the still 1 by means of a vapor line 3 and a condensate run-back line 4, a fractionating tower 5, a condenser 6 and a receiver 7, an evaporator 8 and 75 a condenser 9. The still 1 comprises adrum, a battery of heating tubes 10 extending through a heating furnace 11 and connected at both ends to the drum, and a circulating impeller 12 arranged to maintain rapid circulation of the still charge through the drum and the heating tubes. Line 13 is provided for pumping out the still at the end of a run and for initially charging the still at the beginning of a run. Line 14 including pressure reducing valve 15 is provided for 85 discharging unvaporized oil from the still 1 to the evaporator 8. Condensation in the reflux `tower 2 is effected and controlled by the regulated introduction of the stock to be treated through line 16, thermostatically controlled 9o valve 1'7 being provided in this line for automatically regulating the introduction of this stock to maintain a constant temperature at the upper end of the reux tower 2. The operation of the fractionating tower 5 is eiiected andcontrolled "5 by the regulatedintroduction of part of the cndensed distillate product through line 18, thermostatically controlled valve 19 being provided in this line for automatically regulating the introduction of this condensate to maintain a constant temperature at the upper end of the iractionating tower 5. Pressure controlled throttle valves 20 and 21 are provided for the pumps 22 and 23 respectively to coordinate the operation of these pumps with the operation ol the valves 17 105 and 19 respectively. Pump 24 is provided with a manually controlled throttle valve 25, being provided with a pressure controlled relie! valve 26.

`Vapors escape from the upper end of the reflux tower 2 through connections 27 and 28 to the 110 lower end of the fractionating tower 5 or through connections 27, 29 and 30 to the condenser 6. Vapors escape from the upper end of the fractionating tower 5, if this fractionating tower is used, through connections 31 and 30 to the condenser 6. Condenser 6 discharges into receiver 7. Uncondensed vapor and gas is discharged from this receiver through connection 32. Condensate is discharged from this receiver through connection 33 into the condensate tank 34 from which the reiined product overflows through connection 35. That part oi this condensate supplied to the fractionating tower 5 through con- `nection 18 by means of pump 23 is withdrawn from 'condensate tank 34 through connection 36. Condensate separated in the fractionatingv tower 5 is discharged through connection 37 and cooler `38, the discharge of this condensate being automatically regulated by means of float controlled valve 39. Bottoms are discharged from the evaporator 8 through connection 40 and vapors are discharged from this evaporator through connection 41 and condenser 9. Pressure in the still 1 is maintained and regulated by means of valve 42 or valve 43. The still 1, the evaporator 8, the reiiux tower 2, the fractionating tower 5 and the several hot connections are with advantage thermally insulated to minimize heat loss.

In one way of carrying out the invention in apparatus of the type illustrated, the still 1 is rst charged, through connection 13, with somewhat less than a normal operating charge of a stock mixture including 25-35% of gasoline boiling oil at 410 F. under atmospheric pressure together with gas oil character components. This raw stock mixture, for example, mayconsist of a raw unfractionated condensate discharged from a vapor phase cracking operation carried out to produce gasoline from gas oil or the like. The impeller 12 is then started and with the vapor line comprising connections 27, 29 and 30 open to the condenser, lines 13 and 14 being closed, the still is ilred .and the heating oi' the still charge is so continued until distillate begins to collect in the receiver 7. The valve 43 is then closed and the heating continued until the pressure in the still 1 reaches, for example, about 100 pounds'per square inch. The valve 42 is then gradually opened so that the vapors from the reilux tower 2 escape through thefractionating tower 5 to the condenser 6. From this point on during the operation, a pressure approximating 15-20 pounds per square inch is maintained in the receiver 7 by regulating the discharge of uncondensed vapors and gases therefrom. T'he valve 42 is gradually opened until the pressure in the still reaches, for example, 150 pounds per squareinch and is then regulated to maintain a constant pres'sure in the still 1. When the temperature at the upper end oi! the reilux tower 2 reaches 50o-550 F. the introduction of the raw stock mixture through connection 16 is begun and regulated to maintain .this temperature constant. Similarly when the temperature at the upper end of the fractionating tower 5 reaches Z50-275 F., the introduction of condensate through connection 18 is begun and regulated to maintain this temperature constant. During this period of operation the charge of oil circulating in the still 1 gradually builds up to a normal operating charge and .at this point the discharge of unvaporized oil through line 14 is begun and regulated to maintain this charge constant. 'I'he operation is then continued in this manner until the still is shut down for cleaning.

Instead of initially charging the still with the raw stock or stock mixture including the gasoline to be treated, the still may be rst charged with a gas oil stock, for example, and the raw stock or stock mixture including the gasoline to be treated then supplied when the still is brought to operating conditions.

Although the use of lime is not essential to the invention, the still seems to remain clean for longer periods of operation if a small amount of lime is supplied to the still in dispersion in the raw stock. To accomplish this end, from 1/2 to 11/2 pounds of lime per barrel (42 gallons) of raw stock, for example, may be supplied to the operation. This lime is conveniently mixed with or dispersed in a small part of the raw stock supplied to the operationv and this mixture or dispersion then introduced, by means of pump 24, into the main stream of raw stock flowing through connection 16.

Upon reduction of pressure as it passes the pressure reducing'valve 15, the unvaporized oil discharged from the still 1 through line 14 separates into a vaporized fraction and a bottoms. This vaporized fraction consists mainly of the higher boiling components of the raw stock or stock mixture supplied to the operation and is condensed in the condenser 9. '.Ihe bottoms, discharged through connection 40, is an oil mixture of low viscosity and having a low cold test suitable for use as fuel oil.

The operation of the fractionatlng tower 5 is advantageously regulated, with respect to the operation of the reflux tower 2, so that a relatively low boiling gasoline fraction is collected in the receiver 7 and so that the condensate fraction discharged through connection 37 includes a relatively high boiling gasoline fraction. The condensate fraction may then be subjected to doctor or other sweetening treatment and redistilled'for the separation of its gasoline content and this gasoline fraction then combined with the directly 'separated relatively low boiling gasoline fraction. Or the operation of the fractionating tower 5 may be regulated so that the total gasoline fraction of the vapors from the reilux tower 2 is collected as a gasoline product in the receiver '1. Again, the vapors from-the reilux tower 2- may be discharged directly to the condenser 6 and a composite condensate of the total vapor mixture collected in the receiver 7 and this condensate, after any desired further treatment, redistilled for the separation of the gasoline fraction.

Applying the invention in this manner in apparatus of the type illustrated to a raw stock mixture boiling off 20% at 390 F., 40% at 448 F., 60% at 468 F. and 80% at v521 F., containing about 25-30% of a raw gasoline fraction produced by vapor phase cracking having a gravity of 47 B., a gum content (copper dish test) of 884 mg.

-per 100 cc. and a benzol equivalent of 49% boiling off 90% up to 398 F., a refined gasoline fraction having a gravity of 47.9, a gum content of 371 Ing. per 100 cc. and a benzolequivalen't of 43% boiling off 90% up to 396 F., for example, has been produced in regular commercial operation, the rened gasoline product having high antiknock value and being sufllciently stable, from the standpoint of gum formation or separation, for distribution and use as motor fuel in the regular course of business.

The process of the invention is with advantage rso I 1,969,047 combined directly with the severe cracking operation producing the raw gasoline stockor raw gasoline-containing stock to be treated. The

` higher boiling components required in carrying out the present invention may then be supplied to the refining operation as the higher boiling components produced in the severe cracking operation, the vaporproducts from the severe cracking operation being condensed to form a condensate including the gasoline fraction' and the higher boiling fraction. For example, a gas oil stock may be supplied to a vapor phase cracking operation in which it is heated to a temperature upwards of 10001100 F. under atmospheric pressure or a somewhat higher pressure and the vapor products from this operation, after separation of any tarry residue produced in the operation, condensed in toto to forma composite condensate including the gasoline fraction and the higher boiling fraction and this .composite condensate then supplied to the refining operation of the present invention. The higher boiling components of such a stock mixture, having been subjected to severe cracking conditions, are relatively refraci tory with respect to further cracking, so that the charge of of oil in the still in which the operation of the present invention is carried out may be heated, when such a stock mixture is supplied to the reiining operation, to a relatively high ternperature promoting polymerization of gum and gum-forming constituents before any substantial' cracking of this stock begins.

- I claimz 1. In refining gasoline produced by severe cracking and containing substantial quantities of gum or gum-forming constituents, the improvement which comprises maintaining a body of oil including a major portion of oil components higher boiling than suitable as components of gasoline and having a solvent capacity for such gum or gum-forming constituents under substantial superatmospheric pressure and at a poly'- merizing temperature upwards of-about 650 F. but below that at which any substantial cracking of stock supplied to the operation begins by continuously heating said body by means independent of the supply of fresh stock thereto, during said heating operation supplying a stock including a substantial proportion of said gasoline components produced by severe cracking and such higher boiling components of saidoil body, continuously taking off vapors including gasoline components from said body of oil and subjecting these vapors to a refluxing operation from which condensate is returned to the said body of oil being heated, continuously taking ofi vapors including gasoline components from said refiuxing operation and collecting a refined gasoline fraction therefrom, and during said heating operation discharging unvaporized oil including gum constituents andl polymers of such gum-forming constituents in solution from said body of oil.

2. In refining gasoline produced by severe cracking and containing substantial quantities of gum or gum-forming constituents, the improvement which comprises maintaining a body of oil including a major portion of oil components higher boiling than suitable as components of gasoline and having a solvent capacity for such gum or gum-forming constituents under substantial superatmospheric pressure and at a polymerizing temperature upwards of about 650 F. but below that atwhich any substantial cracking of stock supplied to the operation begins by circulating oil from said body through a heating zone and back to said body, continuously heating the oil circulating through said heating zone, during said heating operation supplying a stock including a substantial proportion of said gasoline components produced by severe cracking and such higher'boiling components to said oil body, continuously taking of! vapors including gasoline components from said body of oil and subjecting these vapors to a reiiuxing operation from which condensateis vreturned to said body of oil being heated, continuously taking of! vapors including gasoline components from said reiiuxing operation and collecting a refined gasoline fraction therefrom, and during said heating operation discharging unvaporized oil including gum constituents and polymers of such gum-forming constituents in solution from said body of oil.

3. In refining gasoline produced by severe cracking and containing substantial quantities of gum or gum-forming constituents, theimprovement which comprises maintaining a body of oil including4 a maior portion of oil components higher boiling than suitable as components of gasoline and having a solvent capacity for such gum or gum-forming constituents under substantial superatmospheric pressure and at a polymerizing temperature upwards of about 650 F. but belowthat at which any substantial cracking of stock supplied to the operation begins by passing oil in addition to any fresh stock to be supplied to said body through a heating zone and thence into said body, continuously heating the oil passing through said heating zone, during said heating operation supplying a stock including a substantial proportion of said gasoline components producediby severe cracking and such higher boiling components to said oil body, continuously taking oil vapors including gasoline components from said body o! oil and subjecting these vapors to a refluxing operation, returning condensate from said reiiuxing operation to said body, and causing said condensate to pass through the said heating zone, continuously taking oil vapors including -gasoline components from said refluxing operation and collecting a refined gasoline fraction therefrom and during said heating operation discharging unvaporized oil including such gum constituents and polymers of such gum-forming constituents in solution from said body of oil.

4. In refining gasoline produced by severe cracking wherein the oil to be cracked is subjected to temperatures upwards of approximately 1000 F. said gasoline containing substantial quantities of gum or gum-forming constituents, the improvement which comprises maintaining a body of oil 130 including a major portion of oil components higher boiling than suitable asv components'of gasoline and having a solvent capacity for such gum or gum-forming constituents under substantial superatmospheric pressure and at a moderate cracking and polymerizing temperature upwards of 600 F. by circulating oil from said body through a heating zone and back to said body, continuously heating the oil circulating through said heating zone, during said heating operation supplying a stock including a substantial portion of said gasoline components produced by such severe cracking and such higher boiling components to said oil boda-continuously taking of! vapors including gasoline components from said body of oil and subjecting these vapors to a refluxing operation from which condensate is returned to said heated body of oil, continuously taking off vapors including gasoline components from said reuxing operation and collecting a rened gasoline fraction therefrom, and,during said heating operation discharging unvaporized oil including such gum constituents and polymers of such gum-forming constituents in solution from said body of oil. l

5. In refining gasoline produced by severe cracking and containing substantial quantities of gum or gum-forming constituents, the im' circulating through said heating zone, during said heating operation supplying a stock including a substantial proportion of said gasoline components produced by severe cracking and such higher boiling components to said oil body, said stock having lime dispersed therein, continuously taking off vapors including gasoline components from said body of oil and subjecting these vapors to a reiiuxing operation from which condensate is returned to said body of oil being heated, continuously taking off vapors including gasoline components from said refluxing operation and collecting a renecl gasoline fraction therefrom, and during said heating operation discharging unvaporized oil including gum constituents and polymers of such gum-forming constituents in solution from said body of oil.

KENNETH J. SMITH. 

